1. Field of the Invention
The present invention relates to a display panel.
2. Description of the Related Art
In a display panel having a capacitive touch panel over a display region, the display region can be viewed through the capacitive touch panel (hereinafter simply referred to as “touch panel”), and a predetermined location on the display region can be designated through, for example, contact of a finger or the like on the touch panel.
In the touch panel, a plurality of X electrodes and a plurality of Y electrodes are formed with an insulating film therebetween in a shape crossing each other, and a change of a capacitance due to contact of a finger can be detected. That is, the touch panel is configured to detect a difference between a capacitance when no finger is in contact (for example, a capacitance Cx of X electrode) and a capacitance when a finger having a capacitance Cf is in contact (Cx+Cf).
Here, when a detection circuit which uses a low current source or the like is used for detection of the change in the capacitance, the signal corresponding to the difference is approximately proportional to Cf/{Cx×(Cf+CX)}. A position (coordinate) of the contact position is calculated through a center-of-gravity process or the like based on this signal, and information is reflected on the display panel.
A touch panel having such a structure is disclosed in, for example, Japanese Application of Unexamined PCT Patent Application No. 2003-511799.
As shown in FIG. 15 which schematically shows a structure of the touch panel, an X electrode XP comprises a plurality of electrodes which extend along a y direction in FIG. 15 and which are aligned along an x direction, and a Y electrode YP comprises a plurality of electrodes which extend along the x direction and which are aligned along the y direction.
The X electrode XP is formed such that a wide-width portion (pad portion) having a rhombus shape and a narrow-width portion (narrow line portion) are alternately provided along the direction of extension of the X electrode XP. Similarly, the Y electrode YP is formed such that a wide-width portion (pad portion) having a rhombus shape and a narrow-width portion (narrow line portion) are alternately provided along the direction of extension of the Y electrode YP.
The pad portion of the X electrode XP and the pad portion of the Y electrode YP are placed so that they do not overlap each other, and the crossing section between the X electrode XP and the Y electrode YP is located at a position of the narrow line portion.
As shown in FIG. 16 which is a cross sectional view along the XVI-XVI line of FIG. 15, the X electrode XP and the Y electrode YP are formed over a substrate TSB with an insulating layer INS therebetween. In FIG. 16, reference sign GRD represents a protection layer for protecting the electrode and reference sign SLD represents a shield layer for blocking noise.
In order to improve the detection capability of the touch panel, it is required that a space α of a certain degree (refer to FIG. 16) be provided between the pad portion of the X electrode XP and the pad portion of the Y electrode YP, when viewed from the top.
In this case, if the space α is widened, there is a disadvantage that, because of a difference in transmittance of light between the portion of the space and the portion where the electrode is formed or because of a difference in a reflective characteristic caused by a difference in the vertical structure as shown in FIG. 16, the pattern of the X electrode XP or the pattern of the Y electrode YP is viewed.
If, on the other hand, the space α is narrowed, and an overlap occurs between the X electrode XP and the Y electrode YP due to a deviation of a mask during manufacturing, the electrode capacitance (Cx or Cy) is significantly increased, and there is a disadvantage that the above-described detection signal proportional to Cf/{Cx×(Cf+CX)} becomes small. In addition, even when there is no overlap between the X electrode XP and the Y electrode YP, when the space α is significantly reduced, a fringe capacitance between the electrodes is increased, resulting in the disadvantage as described above, and degradation in the detection capability of the touch panel.